When scanning PET/CT, dose not unwrinkle gastric folds can be difficult to diagnose gastric cancer. In this study, we use an blowing agent to evaluate the extension the stomach and usefulness of it. The study enrolled 30 patients who patient with uptake in stomach between January and February 2013. Stomach extension was described as the vertical length of the Water drink group was 61.7±9.7 mm, horizontal length was 102.5±17.6 mm and the vertical length of the Blowing agent group was 74.1±10.7 mm, horizontal length was 101.5±14.8 mm in transverse section. Stomach extension was described as the vertical length of the Water drink group was 109.3±18.8 mm, horizontal length was 62.7±18.4 mm and the vertical length of the Blowing agent group was 123.1±23.1 mm, horizontal length was 87.6±14.9 mm in coronal section. Water drink group SUV decreased 35% and Blowing agent group SUV decreased 56%. Blowing agent group extension was similar or superior than water drink group. Therefore, when using a blowing agent will be able to help clinical.